Collapsible pit prop and the like



W- SYLVESTER COLLAPSIBLE PIT PROP AND THE LIKE July 23, 194%.

Filed July 50, 1938 Patented July 23, 1940 UNITED STATES COLLAPSIBLE PITPROPIKND THE Walter Sylvester, Sco tia Works, Tunstall, EnglandApplication July- 30, 1938, Serial No. 222,193 In Great Britain April29, 1938 8 Claims. (01. 248 -351) and is so positioned when attached,that the first M This invention relates to collapsible pit props of thekind having a movable head with an inclined (flat or curved) lowersurface engaging a complementary surface on the end of the prop, andhaving locking means to secure the head in position on the end of theprop, the inclination of the said surface being such that the movementof the head down the surface shortens the effective length of the propto enable withdrawal. Whilst themost general use ofv these props is in avertical position with the head uppermost, as roof supports in mines,they are of course capable of use as thrust membersin otherdispositions, for instance, as horizontal stays in a trench orexcavation, but to achieve clarity of description will be referred toonly in connection with their use vertically. The invention isapplicable to wedge-type props and also to those .not of that type, andmay be applied to props having posts of H section or of round, square orother section.

The primary essentials ina pit prop are .(a) .its safety factor, i. e.,its ability to support a heavy load, (b) its ability to withstand therough usage andabuse which obtains in a coal mine or the like, and (c)the readiness with which it may be set up and removed.

. The main object of the. present invention isto provide constructionsof collapsible pit props Whose load-carrying power is high but which maywhen desired be collapsed with the expenditure of very little energy;which cannot be set up to support a heavy load until locked againstcollapsibility; and which require to be unlocked before any, strong.pull (which might damage the locked prop) can be exerted on thecollapsing mechanism.

According to the invention, the improved prop is characterised in thatthe locking means comprises one or more catches engaging a part .of .thehead and pivotally mounted so that the headengaging surface of eachcatch moves simultaneously with and away from the co-acting part of thehead as the head moves on its inclined surface. Preferably the catch isin the form of alever.

According to a further feature of the inventionthe locking means alsocomprises a twopurpose member adapted in one position to prevent releaseof the catch or catches, and adapted also, when removed from thatpositionto connect pulling mechanism to the catch or catches.

The, invention may be still further characterised in that'the part ofthe pulling means to be attached .to the catch orcatches is so shaped,

hook 6 adapted to enter and pass through a hole in the extending part ofthe plate 2. The lower level than the flange 9 ments of the retainingplate 9, when the lever 5 pull releases the catch or catches from aretaining member, which previously was locked by the said two-purposemember.

The invention is illustrated in the accompanying drawing, wherein:

Fig. 1 is a side elevation of the upper part of a wedge-type collapsibleprop in a locked condition;

Fig. 2 is a front elevation of the same; n

t Fig. 3 is an elevation of the same from the opposite side to Fig. 1,but in the collapsed position; v

Fig, 4 is a fragmentary side view showing the operation of the pullingmechanism .to release the catch; and

Fig. 5 is a side viewiof a modification hereinafterdescribed. Referringto Figs. 1 to 4, the prop comprises a per end of the strut l is cut atan angle and a plate '2 is welded thereto so as to provide a flatinclined surface, the plate 2 extending beyond the strut at the front,and the extending part being supported by the webs orbrackets 3 weldedtheretoand to the strut. The upper corner of the plate at the lower edgeis rounded (see Fig. 1) to facilitate the final movement of the head.

In the webs 3 is. journaled a pivot pin 4 for .a locking lever 5, thepivoted end of the lever being of flat disc formand having a beak or endof the lever 5 is cranked inwardly at 6 and has a through hole 1, itsextreme lower end lying against the front flange of the strut I betweenL shaped guides 8 welded to such flange.

Slida-ble in the L shaped guides 8 is a re- .taining plate 9, the centreportion of which is outwardly bent so as to bridge over the tail end ofthe lever 5. Such plate 9 has an inwardly directed flange 9%, which liesbelow the tail of the lever 5, and is obstructed thereby, and also has adownwardly extending skirt, at a lower Rivets ID in the front flange ofthe prop limit the up and down moveis lifted away from'the strut.

Placed in a hole in the front flange of the strut is one arm ll of aright-angled pin, the other arm I2 of. which, when vertical, liesagainst .the .strutand projects .upbehindthe skirt of the plate 9, andalso supports that plate by the flange 9 The locking lever 5 is ofrobust structure formed with its central portion adapted to serve as ahand grip or handle.

The head is of box-like form having an inclined lower plate I3 to lie onand slide down the inclined surface 2 on the end of the post, and alsohaving sides I4 to locate it on the post. In the construction shown, thehead comprises the two side plates I4, each creased to receive theinclined plate I3, and a surrounding band I5 at the top, the whole beingwelded together. Placed in .the upper end of the head is the loose blockor cap I6, the complete removal of which is prevented by the attachedstops II which are obstructed by the band I5, and a wedge IB is providedbetween the plate I3 and the block IS, the wedge being recessed at It*on its sides and being held captive in the head by the screws or pins I9which project into such recesses. The head itself is held captive to thestrut by the screws or pins 20, the ends of which lie between theflanges of the strut and between the plate 2 and cross pieces 2|. Theinclined plate I3 of the head extends beyond the front so as to projectover the extended part of the plate 2, and in such portion of the plateI3 is formed a rectangular slot 22, one edge of which is adapted to beengaged by the beak or hook 6 of the catch lever 5. This edge of theslot is preferably rounded so as to avoid any undue friction or abrasionbetween the hook and the plate during release of the head.

The lever 5 is adapted to be attached at the hole 7 to a shackle 23, oneend of which is formed with a short beak-like part. The shackle 23 maybe placed over the lower end of the lever 5, and the locking pin III2extracted from below the retaining plate 9, and inserted as a pivot toattach the shackle to'the lever. This dual use of the pin ensures thatthe sliding locking piece is free to fall before the shackle can beattached.

In operation, with the parts as shown in Figs. 1 and 2, the locking pinis first rotated to the position shown in dotted lines in Fig. 2,Whereupon it may be withdrawn and allow the retaining plate to fall. Theshackle 23 is now attached to the lever 5 by means of the horizontalpart II of the locking pin and a pull is exerted on the shackle by meansof the attached chain. The beak-like part of the shackle, as the shackleis rotated about its pivot by the pulled chain, engages the top part ofthe retaining plate 9 and displaces it thereby releasing the lever 5which, by the continued pull of the shackle, is rotated about its pivot4 to cause the hook 6 to be drawn into the plate 2 and cease to obstructthe sliding of the head down that plate. It will be seen that the loadbetween the plates I3 and 2 does not in .any way bind the locking hook6, since the unlocking movement of that hook is in the direction whichthe head tends to take under the load.

The pivot of the lever 5. is placed as near as is practicable to thehead-engaging part of the lever, so that the distance between that pivotand the attached shackle may be several times the distance between thatpivot and the head-engaging part, with the result that very little pullon the shackle is suiiicient to withdraw the hook 6 into the plate 2.

In resetting the prop, the head is placed in position on the inclinedplate 2, the lever 5 is closed down against the flange of the strut, theretaining plate 9 israised over the tail end of the lever and thelocking pin II--I2 is inserted in position, first horizontally until itspart I2 engages the strut flange, whereupon it is turned into a verticaldirection so as to lock the retaining plate 9 between itself and thelever 5, whilst being itself locked between the skirt and the strutflange.

In pulling the prop, the catch lever kicks up as soon as the retainingplate 9 releases its tail and thus an instantaneous release is obtained.

The pulling away of the lever 5 before its tail has been unlocked isprevented since the shackle 23 cannot be attached thereto, unless a pinis used as an attachment, and the necessity for such pin reminds theuser that the locking pin III2 needs to be removed.

Referring now to Fig. 5, the head of the prop may, instead of being awelded built-up unit as shown in Figs. 1 to 4, be a cast unit. In suchcase, the head will have a forwardly-projecting part with a slot in itslower face, to be engaged by the hook ii, and will have downwardlyextending side cheeks to embrace the upper end of the strut, such cheekscarrying inwardlydirected pegs or screws to hold the head captive to thestrut. No wedge is employed in this construction.

Instead of the lever 5 and its associate parts being mounted on theouter face of the strut it could be mounted between the strut flanges,and in any case, the method of attaching the sliding retaining plate 9to the strut may take any suitable form, it being quite common inengineering practice to have one member slidable within or on another.

In order to avoid the trapping of the users hands between the head andthe strut as the head falls, a wedge-shaped spacing member 24 is weldedto the side, and limits the downward 'movement of the head so as toleave room between the head and the strut for the users fingers.

The retaining plate 9 may be provided with a spring, or with aspring-loaded ball, to snap into recesses in the front flange of thestrut and prevent the plates falling by its own weight. This wouldensure the locking lever 5 being firmly held until the attached shacklewere pulled to dislodge the retaining plate.

What I claim is:

1. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto contract the length of the prop, a locking lever pivotally mounted onthe strut and having a projection to engage the head and hold it on thesaid inclined end of the strut, the projection and pivot cooperating sothat the projection can move directionally with the head down theinclined end of the strut during the initial movement for disengagementof the projection and head, and a retaining member slidably mounted onthe strut engageable with the end of the locking lever to hold it in thelocking position.

2. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto'contract the length of the prop, a locking lever pivotally mounted onthe strut and having a projection to engage the head and hold it on thesaid inclined end of the strut, the projection and pivot co-operating toallow sliding movement of the head down the inclined end of the strutduringthe disengagement of the projection and head, a retaining memberslidably mounted on the strut engageable with the end of the lockinglever to hold it in the locking position, and a removable member on thestrut adapted to hold the slidable retaining member in the lever-holdingposition.

3. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto contract the length of the prop, a locking lever pivotally mounted onthe strut and having a projection to engage the head and hold it on thesaid inclined end of the strut, the projection and pivot co-operating toallow sliding movement of the head down the inclined end of the strutduring the disengagement of the projection and head, a rctainingmemberslidably mounted on the strut engageable with the end of the lockinglever to hold it in the locking position, and a removable member on thestrut adapted to hold the slidable retaining member in the lever-holdingposition, the sliding retaining member and removable member co-operatingto hold each other in the lever-locking position, the removable memberbeing rotatable to a position where it is free of the sliding member forremoval.

i. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto contract the length of the prop, a locking lever pivotally mounted onthe strut and having a projection to engage the head and hold it on thesaid inclined end of the strut, the projection and pivot co-operating toallow sliding movement of the head down the inclined end of the strutduring the disengagement of the projection and head, a retaining memberslidably mounted on the strut engageable with the end of the lockinglever to hold it in the locking position, and a removable member on thestrut adapted to hold the slidable retaining member in the lever-holdingposition, in combination with a pulling means attachable to the. lockinglever by the removable member whereby attachment of the pulling meansentails release of the retaining member.

5. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto contract the length of the prop, a locking lever pivotally mounted onthe strut and having a projectionto engage the head and hold it on thesaid inclined end of the strut, the projection and pivot co-operating toallow sliding movement of the head down the inclined end of the strutduring the disengagement of the projection and head, a retaining memberslidably mounted on the strut engageable with the end of the lockinglever to hold it in the locking position, and a removable member on thestrut adapted to hold the slidable retaining member in the lever-holdingposition, in combination with a pulling means attachable t0 the lockinglever by the removable member when the latter is removed to release thesliding retaining member, whereby attachment of the pulling meansentails release of the retaining member, the pulling means comprising ashackle to embrace the locking lever and so shaped that when pulled itfirst engages and displaces the sliding member to release the lockinglever, and then rotates the locking lever to release the head.

6. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto contract the length of the prop, a locking member on the strut toengage the head and obstruct its sliding movement, latching means on thestrut to prevent unlooking of the head, and pulling means for firstunlatching the locking member, and then unlocking the head by retractingthe locking member out of the path of the head in a direction permittingsimultaneous sliding movement of the head.

7. A collapsible pit prop according to claim 1,

wherein the head comprises metal side cheeks .mentioned plate, suchlever having a hook-like extension to pass through the apertures in thetwo plates to lock them together.

8. A collapsible pit prop comprising a strut with inclined upper endface, a head shaped to fit over such inclined face and to slide down itto contract the length of the prop, a locking lever pivotally mounted onthe strut and having a projection to engage the head and hold it on thesaid inclined end of the strut, the projection and pivot co-operating toallow sliding movement of the head down the inclined end of the strutduring the disengagement of the projection and head, a retaining memberslidably mounted on the strut engageable with the end of the lockinglever to hold it in the locking position, and a removable member on thestrut adapted to hold the slidable retaining member in the lever-holdingposition, in combination with a pulling means attachable to the lockinglever by the removable member whereby attachment of the pulling meansentails release of the retaining member, the removable member comprisinga lever having a pivot pin attached to it, said pivot pin being ofsuitable size in diameter and length for use for connecting the pullingmember to the locking lever.

WALTER SYLV'ESTER.

